The use of potent and expensive chemicals for the control of molds, bacteria, insects, undesirable vegatation, soil fertility, corrosion, algae and the like has been known for years. Early methods of applying such chemicals relied on the sprinkling of powders or granules to control the amount of chemical delivered to the desired site. Later inactive diluents were used to dissolve and thereafter deliver the reagent. While somewhat effective, the distribution of solid chemical or dissolved chemical was not cost effective because some areas received too much and other areas received too little of the active ingredient.
With the advent of liquid pumping systems, it became possible to mix the active chemical with water. The water solution or suspension could be distributed by spraying the area to be treated. However, thorough mixing of active chemical into the carrier stream still posed a problem because even a small error in measurement or insufficient mixing could cause over or under treatment and frustrate the desired effects.
As previously stated, the use of liquid dispersal systems was somewhat effective, allowing for the difficulty in accurate mixing and brought the incorporation of venturi tubes within the carrier stream path as shown in U.S. Pat. No. 4,123,800, Mazzei. While Mazzei somewhat alleviated the mixing problem, the device did not permit the vaccum created thereby to be controlled with the end result that the mixer either operated at its optimum or it did not operate at all.
Thus the art as developed is unable to precisely and incrementally meter chemical additives into a flowing carrier stream. It is toward the solution of that problem that the present invention is directed.